The present invention relates to a diversity receiver and, more particularly, to a diversity receiver which has two radio receivers and performs selective switching between demodulated outputs from the two radio receivers.
Conventionally, diversity receivers of this type can be grouped into those of a selection diversity type and those of an antenna diversity type. A selection diversity-type receiver has two radio receivers (referred to as "receivers" hereinafter), each of such receivers having an antenna and amplifier. The receiver demodulates an input signal received by its antenna in order to output a demodulated signal when it is supplied with power (i.e., is switched ON) and generates an electric field intensity output in accordance with the intensity of the electric field. The selection diversity-type receiver; compares the electric field detection outputs from the two receivers while the two receivers are constantly ON, and performs switching in order to select a demodulated output from a receiver having a higher electric field detection output. When the intensity of the received electric field is high, since the degradation in S/N ratio of the reception signal due to fading is small, no advantage is obtained in performing diversity signal reception. Despite this, in the conventional diversity receiver, the power sources for the two receivers are constantly ON regardless of the intensity of the received electric field. Therefore, when the intensity of the received electric field is high, excessive power is consumed.
In an antenna diversity-type receiver, any of a plurality of antennas is connected to a single receiver. When the quality of communication of the selected antenna is degraded below a predetermined value, it is switched to another antenna, thereby restoring predetermined quality of communication. Since only a single receiver is provided, power consumption is small. However, quality of communication is not so improved much as in the selection diversity-type receiver.